“While email worms occupy the top spots, it’s clear that Trojans represent by far the most prominent threat to IT security,” said Carole Theriault, senior security consultant at Sophos.
Netsky is still the most common virus seen online, accounting for about one in five of all viruses despite a fix and removal tools being widely available for more than two years.
“The expected reign of IM worms has not arrived because virus authors are confronted with a fundamental barrier when engineering an IM worm,” stated Fortinet’s report. “While email addresses are easy to collect on the web, instant messaging IDs are generally less public, making the seeding process significantly harder to set up.”
http://www.vnunet.com/vnunet/news/2155151/viruses-longer-top-threat-april